In general, metered-dose inhalers (MDIs) are devices for dispensing medicaments, e.g. in aerosol form, to the lungs. Broadly speaking dispensers such as MDIs are comprised of two components: a container and a delivery device. The container holds the medication, e.g. dissolved or suspended in a propellant under high pressure to maintain a liquid phase. Additionally the container often comprises an internal metering valve, which is designed to release a precisely measured, reproducible dose of medicament when the valve is actuated. The delivery device typically includes an actuator and a mouthpiece. The actuator, which can be triggered by the user, for example by inhalation or manual operation, typically interacts with the metering valve of the container to induce release of a dose. The mouthpiece serves to direct the medication towards the user.
We have previously described a number of dispensers, see for example U.S. Pat. No. 7,721,731 and WO 2013/064821. We have also described a dispenser cap arrangement, see WO 2013/064820. We have also disclosed dosage counters for use with such dispensers, see for example WO 2010/103315. Further examples of dose counters and dispensers may be found in WO2005/060535, GB2372542 and US2011/259324.
As medicament containers are typically made of an opaque material such as aluminium, and may be housed entirely within a delivery device, it is generally not possible for a user to gauge effectively how many doses of medicament remain therein. This may result in a user prematurely discarding a MDI still containing doses of medicament or worse using the MDI beyond its recommended lifetime. Neither situation is desirable—the former is wasteful while the latter is potentially dangerous. Users sometimes shake MDIs to try to obtain a measure of whether any medicament is present therein, but this only provides a very crude qualitative measure of the container contents. It would not, for example, enable a user to distinguish between a container comprising enough medicament and propellant to form a dose and one comprising a quantity of medicament and propellant that is less than that needed to fill the metering valve. In other words, there is a risk that users overestimate the amount of medicament present in a container and mistakenly conclude that there is sufficient medicament remaining for another dose when in fact there is not. Additionally a user may not be provided with sufficient warning to obtain a replacement medicament container prior to the one in use running out.
It is therefore desirable to provide dispensers, e.g. inhalers, with a counter mechanism that enables a user to track how many doses have been dispensed therefrom and, complementarily, how many doses remain. Indeed, regulatory bodies such as the Food and Drug Administration (FDA) of the United States and the European Medicines Agency (EMEA) have issued guidelines encouraging the implementation of dose-counters (Food and Drug Administration, “Guidance for industry: integration of dose counting mechanisms into MDI drug products”, 2003; European Agency for Evaluation of Medicinal Products, “Final guideline on the quality of inhalation and nasal products”, 2005).
Dose counters can generally be classified according to the manner by which a ‘count’ is registered, these being mechanical counters comprised of a series of moving parts that respond to a movement or mechanical force resulting, for example, in a displacement of the container/housing; electronic counters having electrical circuitry to sense an event associated with an actuation such as sound, temperature or pressure change; and electro-mechanical counters which combine electrical and mechanical parts.
Some background prior art relating to dose counters includes: EP1169245 Dispensing Apparatus Comprising a Dosage Counting Device; PCT/GB97/03480 Inhaler Dose Counter; PCT/US1996/008418 Indicator Device Responsive to Axial Force; PCT/FR2004/001844 Improved Dose Indicator for Fluid Product Dispensing Device; GB2372542 Dosage Counting Device; PCT/CA04/001884 Indicating Device with Warning Dosage Indicator; PCT/US04/039926 Dose Counter for Dispensers; and U.S. Pat. No. 7,047,964 Dispenser for Medicament.
Other developments in the field of dose counters include Bang & Olufsen Medicom's ‘Insulair’ (Trade Mark) device, and the disclosures of: WO 98/056444 Dispenser with Doses Counter; WO 04/001664 Actuation Indicator for a Dispensing Device; WO 07/012854 Canister-Supported Rotating Ring Count Readout Assembly for a Metered Dose Inhaler; and DE 10061723 Zählwerk zum Zählen dosierter Abgaben flüssiger oder fester Produkte sowie Einrichtung zum dosierten Abgeben solcher Produkte.
It has been found that, during use of the dispenser and counter, manufacturing tolerances may in some instances affect the performance. For example, it has been found that manufacturing tolerances mean that the length of a container or substance source can vary from container to container. Furthermore, the length of the spout of the container may vary, too.
This can cause problems in dispenser devices wherein the aerosol can is stationary and another part is moved relative to the can to displace its valve and dispense medicament. Typically the other moving part can only move a certain distance (i.e. a predetermined amount of travel) which means that if, for example a can or its valve is relatively short, the valve may not be fully displaced. As a result, a full dose of medicament may not be dispensed.
There have been different approaches taken to overcoming this problem. See, for example, WO2003/080161 or WO2007/029019.
In the above-mentioned previous approaches, the dispenser body and cap are a constant size and the canister is placed in the body at the same position in all dispensers. The variation in the resulting space between the end of the canister and the cap is taken by deformable materials placed atop the container. However, the above solutions do not always provide satisfactory results.
Furthermore, with reference to the counter, it has proven difficult to provide dose counters that reliably “count” the release of medicament doses from containers. The difficulty encountered is that a relatively small movement, typically of the metering valve stem, needs to be detected and translated into a count. This difficulty is exacerbated by manufacturing tolerances in the length of medicament containers which means they do not have a consistent length, and also manufacturing tolerances in the dimensions of the components comprising the counter mechanism and its coupling to the dispenser mechanism. At the same time, it is highly undesirable for any movements to not be counted since this will lead to the counter indicating a higher number of doses remaining than is actually the case. Moreover there is also regulatory pressure to minimise the number of false counts.
As such, we have appreciated the need for an improved dispenser.